“I'm kidding, you don't understand sarcasm,” the president said.
The president spent about 50 minutes on the White House lawn speaking to Fox News and other reporters in the unexpected appearance.
North Korea has perpetuated human rights abuses for decades, according to human rights groups and the U.S government.
In his first five years in power, Kim has ordered 340 people to be executed. About 140 were senior officers in the country's government and military, according to a 2016 report from the Institute for National Security Strategy, a South Korean think tank.
Trump was later asked about how he was able to mourn the death of American Otto Warmbier, who was held hostage in North Korea and died after his release, while defending Kim Jong Un’s leadership and human rights record.
“I don't want to see a nuclear weapon destroy you and your family,” Trump said. “I want to have a good relationship with North Korea. I want to have a good relationship with many countries.”